Some Basic Concepts of Chemistry Test

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Some Basic Concepts of Chemistry Test - 33

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Weekly Quiz Competition

Question 1
1 / -0

Calculate the % composition of Carbon in $$CO_2$$. Molar mass is 44.01.

A
40%

B
67%

C
30%

D
27%

Solution

Molar mass of compound:
Mass due to carbon: 12.01 g/mol
Total molar mass $$= 12.01 + 2(16.00) = 44.01g/mol$$ ($$CO_2$$ has two $$O_2$$ atoms)
Percent composition of carbon: $$12.01/44.01 \times 100 = 27.28$$%
Question 2
1 / -0

A solution is prepared by dissolving 60 g of sodium chloride in 400 g of water. What is the mass-by-mass percent of sodium chloride in this solution?

A
18%

B
13%

C
0.13%

D
0.15%

Solution

Mass of NaCl dissolved $$= $$ 60 g
Mass of water taken $$=$$ 400 g
Total Mass of solution $$= 400 + 60 = 460\ g$$

Mass / Mass % of NaCl in solution $$= \dfrac{\text{Mass of NaCl} \times 100}{\text{Mass of solution}}$$

$$= \dfrac{60 \times 100}{460} = 13.04$$%
Question 3
1 / -0

The mass of a sand and powdered mixture along with a beaker is 56 g. If the mass of the dried mixture is 20 g, find the % composition of the mixture in 100 g?
(weight of beaker = 20 g).

A
20%

B
36%

C
55%

D
60%

Solution

Mass of beaker = 20 g
Mass of mixture + beaker = 56 g
Mass of mixture = 56 - 20 = 36 g
Mass of washed and dried sand = 20 g
100 g of mixture contains $$= \dfrac{20}{36} \times 100 = 55$$% of sand
Question 4
1 / -0

Which law was given by Antoine L. Lavoisier?

A
Laws of multiple proportion

B
Law of conservation of mass

C
Both A and B

D
None of the above

Solution

Antoine-Laurent Lavoisier established the law of conservation of mass.
It states that "mass can neither be created nor be destroyed in a chemical reaction."
So, the correct option is $$B$$.
Question 5
1 / -0

If the % composition of a 'x' component is 35%, find the mass of the dried 'x' component in 100g? mixture + beaker = 50 g, mass of beaker = 23 g

A
15.5 g

B
9.45 g

C
35.5 g

D
13.4 g

Solution

mass of beaker $$= 23g$$
mass of mix + beaker$$ = 50g$$
mass of mixture $$= 50 - 23 = 27g$$
$$\%$$ composition of mixture $$= 35\%$$
Mass of the x component $$= 35 \times \dfrac{27}{100} = 9.45g$$
Question 6
1 / -0

A sealed tube containing phosphorus was weighed and heated carefully. After completion of the reaction, the tube was re-weighed under similar conditions. The weight of the tube will:

A
increases

B
decreases

C
remains same

D
None of the above

Solution

According to the law of conservation of mass, the total mass of reactants is equal to the total mass of products in a chemical reaction.

$$P_4 + 5O_2\rightarrow P_4O_{10}$$

As the tube is sealed, the total mass of reactants, $$P_4$$ and $$O_2$$ is equal to the total mass of product formed i.e., phosphorus pentaoxide.
Question 7
1 / -0

According to Dalton, atom combines in a _________ ratio to form compounds.

A
variable

B
fixed

C
Both A and B

D
None of the above

Solution

According to Dalton, atom combines in a $$\text{ fixed}$$ ratio to form compounds.
option $$B$$ is correct.
Question 8
1 / -0

Determine the percentage composition of $$K$$ in $$KMnO_4$$.

A
$$31\%$$

B
$$43.58\%$$

C
$$25\%$$

D
$$55\%$$

Solution

To find:- $$\%$$ composition of K in $$KMnO_4$$
A/c
Molar mass of $$K=39$$g
Molar mass of $$KMnO_4=158$$gm
$$\%$$ of k in $$KMnO_4=\dfrac{39}{158}\times 100=24.68\%$$
$$\approx 25\%$$.
Option C is correct.
Question 9
1 / -0

If the % composition of Cl in HCl is 46%, what is the mass of Cl in HCl?

A
13.3 g

B
66 g

C
25 g

D
16.76 g

Solution

$$\%$$ $$ composition =\cfrac{Mass \quad of\quad an \quad element.}{Total \quad mass \quad of\quad compound.}$$
$$Total \quad mass\quad of\quad HCl=1+35.5 g=36.5g$$
$$\therefore$$ $$\cfrac{46}{100}=\cfrac{mass\quad of\quad Cl}{36.5}\\ mass\quad of\quad Cl=16.76g$$
Question 10
1 / -0

Law of conservation of mass is also known as :

A
Law of indestructibility

B
Law of mass action

C
Law of conservation of energy

D
None of the above

Solution

Law of Conservation of mass is also known as Law of indestructibility because the mass is conserved and it proves that matter is always conserved and can never be destroyed.

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Some Basic Concepts of Chemistry Test - 33

Result

Some Basic Concepts of Chemistry Test - 33

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SHARING IS CARING

Question 1

40%

67%

30%

27%

Solution

Question 2

18%

13%

0.13%

0.15%

Solution

Question 3

20%

36%

55%

60%

Solution

Question 4

Laws of multiple proportion

Law of conservation of mass

Both A and B

None of the above

Solution

Question 5

15.5 g

9.45 g

35.5 g

13.4 g

Solution

Question 6

increases

decreases

remains same

None of the above

Solution

Question 7

variable

fixed

Both A and B

None of the above

Solution

Question 8

$$31\%$$

$$43.58\%$$

$$25\%$$

$$55\%$$

Solution

Question 9

13.3 g

66 g

25 g

16.76 g

Solution

Question 10

Law of indestructibility

Law of mass action

Law of conservation of energy

None of the above

Solution

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